Method for making inner molds



Cd- 14, 1952 E. M. CROWELL METHOD FOR MAKING INNER MOLDS 2 SHEETS-SHEET 1 Filed Dec. 10, 1947 Inventor Ernest M Crow/ell;

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Oct. 14, 1952 2,613,398

E. M. CROWELL METHOD FOR MAKING INNER MOLDS Filed Dec. 10, 1947 2 SHEETS-SHEET 2 K gs Q Inventor Ernesi M Crow/ell Patented Oct. 14, 1952 METHOD FOR MAKING INNER MOLDS' Ernest M. Crowell, Beverly, Mass, assignor to United Shoe Machinery Corporation, Flemington, N. J a corporation of New Jersey Application December 10, 1947, Serial No. 790,894

8 Claims. (01. 18--55.05)

This invention relates to the manufacture of inner molds for shoes and it is illustrated herein with reference to improved methods and compos itions for making such inner molds.

The making of inner molds of the type with which the present invention is concerned is disclosed in the patent to MacDonald No. 2,138,974 of December 6, 1938. The method of the patent includes the steps of reproducing in greater or less detail the shape of the bottom of a foot and the shape of the exposed surface of an innersole, and using these reproductions as molding surfaces for shaping a plastic mass. The plastic mass, shaped. according to the process of the patent, is a mixture of cork and a pyroxylin solution. After shaping, the mass is set aside for an extended period to permit evaporation of the solvent to convert the mass to a firm, resilient condition.

It is a further feature of the invention to provide an improved method for shaping a suitable material to form inner molds.

With the above and other features in view, the invention will now be described in connection with the accompanying drawings.

In the drawings,

Fig. 1 is a perspective of a rubber bag serving as'a flexible impervious container for a moldable granular mass, the bag being equipped with an end closure and nozzle for removal of air;

Fig. 2 is an elevation of a pressing device in which are mounted shaping members adapted to act on a flexible container partially filled with a moldable mass to shape the plastic mass in order to form an inner mold;

Fig. 3 is an elevation, partly in section, showing the shaping members acting on moldable material confined within a flexible container;

Fig. 4 is a perspective of an inner mold obtained by a shaping operation such as shown in Fig. 3;

Fig. 5 is a perspective of a billet of material, with a slab cut therefrom for use in forming an inner mold;

Fig. 6 is an elevation, partly in section, showing moldable material pressed a ainst a shaping member in an evacuated, flexible container by atmospheric pressure; and

Fig. '7 is a fraction elevation, partly in section,

showing the compression of the moldable material between shaping members wherein lateral expansion of the moldable material is prevented by'adammember.

. In accordancewith. the present invention, a moldable dry mixture of a thermoplastic resin and a shredded cork filler is formed. The mixture is heated to soften the resin, and is shaped by pressing it against a molding surface, whilerestraining it against lateral spreading. The shaped mass is permitted to cool, and when cool is in strong resilient condition particularly suitable for use as an inner mold.

In making inner molds for shoes in one aspect of the method illustrated herein there is prepared a last-like shaping member H! (see Figs. 2 and 3) reproducing in gretaer or less detail the bottom of a persons foot. Suitable methods for forming this member ii] are disclosed in the MacDonald Patent No. 2,138,974, above referred to. There is also prepared a surface member 12 having a contour similar to the upper surface of the inner sole of" the shoe in which the inner mold is to be used. The last-like shaping member ill and surface member l2 are mounted in a pressing device [4 such as that shown in Fig. 2. The pressing device 14 comprises side posts IS, a beam [8 extending across the tops of the side posts, and a table member 28 having guides 22 slidable on the side posts, actuating means (not shown) being provided to raise or lower the table member 20. A bracket 24 for holding the shaping member iii and a support member 26 for the toe portion of the member [0 are slidably mounted ina track 28 secured to the lower side of the beam I3. Setscrews 30 and 32 are provided in the bracket 24 and support member 26, respectively, to hold them in predetermined position. The bracket 24 is provided with a surface 34 parallel to the table 20 for engaging the upper face 36 of the member H]. An expansible pin 38 operated by a lever 40 projects down from the bracket 24' for insertion in the hole 52 in the member Ill to hold the upper face 36 of the member If] against the surface 34 of the bracket 24. The support member 26 for the toe of the member Hi comprises a rounded cushioned presser 44 pivotally mounted on a threaded rod 46 which can be raised or lowered in the baseof the support member by turning the member 41, and may be locked in desired position by a setscrew 48.

Surface member l2 having a surface similar to the upper surface of' the inner sole of a shoe is disposed on table 20. in position directly below the last-like shaping member ID. These members cooperate to shape moldable material 52 disposed therebetween when the table member 20 is raised. Adjustable stops 5!! are disposed on the side posts I6 and are locked on the side posts at a height which will stop further upward movement of the table member 20 when the surface member l2 and last-like shaping member I have been brought together to a position giving a desired thickness to the moldable material 52 bein pressed therebetween.

As shown in Figs. 1, 2 and 3, the moldable material 52 may be confined against undesired lateral spreading under the action of the members l0 and I 2 by positioning it in a flexible container 54 which is illustrated (see Fig. l) as a bag formed of a suitable impervious material such as rubber, synthetic rubbers such as neo-- prene and butadiene acrylonitrile copolymers, or other flexible plastic materials. When the material is disposed in the container 52, the mouth of the container is closed by positioning therein a flat plug member 56 and resiliently pressing the walls of the mouth of the container against the plug 56 by suitable means such as an elastic band 58. the plug member for connection to a conduit 6i leading to a vacuum system (not shown) for removing air from within the container 54.

In the production of an inner mold making use of moldable material 52 disposed in the flexible container 54, the container 54 and material 52 therein is placed on the surface member I0 on the table of the press. The table 29 is then raised to press the container 54 against the bottom surface of the last-like shaping member In to shape the material 52 within the container 54. If desired, this shaping may be improved by hand pressing of the material into more uniform relation with the surfaces of the members [0 and I2. Air is then evacuated from the container by connecting the nozzle 50 with a conduit leading to a vacuum system. The evacuated bag 54 is forced by atmospheric pressure into intimate engagement with the moldable material 52 therein and retains the material 52 in its shaped condition. The nozzle 00 is sealed oif to prevent reentry of air into the container 26 and the table is lowered. The shaped container 54 and moldable material 52 therein are then heated by suitable means to raise the temperature of the mixture to approximately the softening point of the resin of the moldable material. This heating may be done by placing the container 54 in an oven or by placing the container between the electrodes of a highfrequency system or by a combination of these or other known heating procedures. The container and its contents may then be cooled and the shaped material removed for trimming and other operations.

Alternatively, when the moldable material 52 has reached the desired temperature the container 54 and material 52 therein may be returned to position on the shaping member on the table of the press in substantially its original position and the table may then be raised to shape the material 3| between the surface member l2 on the table and the last-like shaping member [0 supported on the beam 18 of the press l4. Approaching movement between the members If! and I2 is stopped when they are at a distance apart which will give an inner mold member of the desired thickness, by contact of the slide members 22 of the table with the stop members 55 which are locked on the side posts IB of the press. The press is retained in closed position until the material 52 within the container 54 has cooled sufficiently to retain its shape when the members It] and I2 are separated. When the material 52 has cooled, and the container 54 and material 52 are removed A nozzle is provided in resin until the mixture is heated;

from the press M, the vacuum on the container 54 is broken, the plug 55 removed, and the shaped material 52 removed from the container. The edges of the shaped material 3| are trimmed oif to form an inner mold 52 such as shown in Fig. 4. The upper and lower surfaces of the inner mold may then be provided with protective fabric covering 64 as described in the Mac- Donald patent above referred to.

In a still further modification of the molding procedure (see Fig. 5) using the flexible container 54, the last-like shaping member ID is covered with a separator film 2'0, for example, a wrapping of cellophane or a thin-walled rubber bag, and is placed within the flexible container A substantial quantity of the moldable material 52 is then placed in the container 54 and disposed along the bottom portion of the last-like member E8. The container 54 is then evacuated so that the walls of the container are pressed by atmospheric pressure against the covered last-like member [5 and material 52, thus pressing and shaping the material 52 against the bottom of the last-like member Ill. The evacuated container 54 containing the covered last-like member l0 and material 52 is heated to a temperature sufilcient to soften the resinous content and is permitted to cool. The vacuum is broken and the last-like member If! and shaped material 52 are removed. The material 52 when shaped under the heat and pressure provides a strip of which one surface reproduces accurately the shape of the bottom of the last-like member ID. The strip is prepared for use as an inner mold by filing, cutting, or otherwise shaping the surface opposite to the surface formed against the last-like member to fit the exposed surface of the innersole of a shoe. The resulting inner mold may be provided with protective fabric coverings on its upper and lower surfaces.

The moldable mixture 52 employed in the present invention comprises a thermoplastic resin and shredded cork of a particle size not larger than that which will pass a ten-mesh screen and preferably of a particle size which will pass a twenty-mesh screen and be retained by a forty-mesh screen. In one mode of preparing the mixture, the shredded cork is mixed with a plasticizer and the mixture of cork and plasticizer is then thoroughly mixed with a finely divided thermoplastic resin. In another mode, there is prepared a plastisol, i. e., a physical mixture of finely divided resin and a latent plasticizer which does not combine with the and this plastisol is thoroughly mixed with shredded cork. Suitable resins for use in the composition of the present invention are copolymers of vinyl chloride and vinyl acetate containing from 88 to 95% of vinyl chloride and having a molecu lar weight above 50,000, ethyl cellulose, cellulose acetate, vinyl butyral, polymerized styrene resins, copolymers of vinyl chloride and vinylidene chloride and other resins. Resins will be selected for use having a melting point above the temperature at which the article comprising resin and cork is expected to function. Compatible plasticizers for the resins will be employed. A suitable plasticizer for use with a copolymer of vinyl chloride and vinyl acetate may be di-2-ethyl hexyl phthalate.

The relative proportions in which the cork resin and plasticizer may be employed are subjected to variation. The cork may be present in percentage of from 20 to the resin from r 5 to 60%;, and, the plasticizer from to 60%,, totaling 100%.. Particularly desirable compositions will contain from 38 to 47% of. shredded cork,.from.22 to 34% ofresin and from 23 to of plasticizer.

In a modification of. applicants method, cork is mixed with plasticizer and then with resin in the proportions above described and the mixture is heated and lightly pressed together to. form a billet. 66', as shown in Fig; 5. Slabs or: rough shapes 68,,suitabl'e for making inner molds, may be cut from such a billet and molded to. desired dimensions. by a pressing procedure. Pressing of the material cut from the billet may be efi'ected by inserting a slab 68 of the cut material into. the. flexible container 54, evacuating the container, heating the evacuated. container, and pressing: the heated material and container between the surface. member l2 and the last-like shaping member In in the press 14'.

In another procedure (see Fig. 7) making use of a slab 68 of material cut from a primary billet 66 of cork, resin and plasticizer, there may be employed, a shaping member 12 on the table 2!! which differs in some respects from the shaping member l2 which may be used with the vacuum bag technique. According to this modification, the surface of the member 12 conforms in some degree to the lengthwise curvingsv of the innersole of a shoe but is substantially flat transversely of the longitudinal axis of the shoe. A. flexible dam T4 is disposed on the surface of this member along a line slightly outside the line formed by the projection of the outline of the last-like member III on the lower shaping member 12.. This dam. may be of the type disclosed in the MacDonald patent. above referred to or may be any other suitable structure capable oi conforming itself" to the simple curve of the lower shaping member 12 and of retaining the shape against. forces tending to move it laterally.

A- slab '68 is heated, placed within the dam, and is given its final shape by raising the table 20 to bring together the last-like member ID and the lower shaping member-"12 as shown in Fig. 6.

Other methods of molding the novel cork resin plasticizer composition may also be employed. For example, a positive mold might be loaded with the loose granular material, the material heated while still in the mold and shaped by cooperation of the last-like member with the positive mold. In this case the material would be cooled while retained under pressure by the last-like member.

Having described the invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. The improvement in methods of making inner molds for shoes which comprises placing a dry granular mixture of shredded cork, finely divided thermoplastic resin and plasticizer in a container having flexible impervious walls, shaping the mixture by a surface approximating the bottom of a foot. removing air from the container to shrink the walls by atmospheric pressure to retain the mixture in the shape imparted to it, removing the container and mixture from contact with said surface while retaining said shape, heating the container and its contents to a temperature sufiicient to soften the resin, and cooling the container and its contents.

2. The improvement in methods of making 6 inner molds for shoes which comprises placing a dry granular mixture of a, finely divided thermoplastic resin, shredded cork and a plasticizer in a container having a flexible, impervious walls, shaping the mixture by pressing the container and mixture therein against a pressing surface reproducing the bottom surface" of a foot, removing air from the container to shrink the walls by atmospheric pressure to retain the mixture in the shape imparted to it, removing the container and mixture from contact with said pressing surface while retaining said shape, heating the container and its contents toa temperature sufiicient to soften the resin, and cooling: the container and its contents.

3. The improvement in methods of making inner molds for shoes which comprises placingin a container having flexible, impervious walls, a dry granular mixture of from 20 to 65% by weight of 20 to 40 mesh shredded cork, from 15 to 60 by weight of a finely divided tough, strong, high-molecular weight thermoplastic resin and from 10 to 60% of a compatiblepIasticizer on the surface of the cork and resin particles, pressing the container and mixture against a pressure surface reproducing the bottom surface of a foot to shape the mixture, removing air from the container to shrink the walls by atmospheric pressure to retain the mixture in the shape imparted to it, removing the container and mixture from contact with said pressing surface while retaining said shape, heating the container and mixture therein to a temperature sufiicient to soften the resin, permitting the resin particles to combine. with the plasticizer to form a plasticized resinous binder, and cooling the container and its contents.

4. The improvement in molding methods which comprises thoroughly mixing from 20% to: 65% by weight of 20-40 mesh shredded cork, from 15% to 60% of an extremely finely divided, tough, strong, high molecular weight thermoplastic resin, and from 10% to 60% of a compatible plasticizer on the surface of the cork and resin particles, placing the mixture in a container having flexible impervious walls, removing air from the container to shrink the walls. and press them against the mixture by atmospheric pres-. sure to hold the particles together and retain the shape of the mass, heating the evacuated container and its contents to soften the resinous material, shaping the mass by pressing the container and mass therein against a shaping surface, cooling the mass, and removing the molded mass from the container.

5. The improvement in methods of making inner molds for shoes which comprises thoroughly mixing from 20 to 65% by weight of 20 to 40 mesh shredded cork with from 10 to 60% of a plasticizer and then with from 15 to 60% of a tough, strong, high molecular weight thermoplastic resin, placing the composition in a container having flexible, impervious walls, roughly shaping the mixture by lightly pressing the container and composition therein between a surface similar to the top surface of the inner sole of a shoe and a surface reproducing the bottom surface of a foot, removing air from the container to shrink the walls by atmospheric pressure to retain the mixture in the shape imparted to it, removing the container and mixture while retaining the rough shape, heating the container and its contents to a temperature sufiicient to soften the resin, placing the container and its contents between the pressing surfaces and bringing the pressing surfaces to a predetermined spaced relation to mold the container and composition to the shapes of said surfaces, cooling the mixture while retaining pressure thereon, removing the container and mixture from between the pressing surfaces, and removing the molded mixture from the container.

6. The improvement in methods of making inner molds for shoes which comprises placing a dry granular mixture of shredded cork, finely divided thermoplastic resin and a plasticizer in a container having flexible impervious walls, inserting a molding surface approximating the bottom surface of the foot in the container, positioning the mixture relative to the molding surface to .supply a substantial thickness of the mixture adjacent the molding surface, removing air from the container to shrink the walls and to press the mixture against the molding surface by atmospheric pressure, heating the container and its contents to a temperature sufficient to soften the resin, and cooling the container and its contents.

7. The improvement in methods of making inner molds for shoes which comprises placing a dry granular mixture comprising from to 65% by Weight of from 20 to 40 mesh shredded cork, from 15 to 60% of fine particles of a tough, strong, high molecular weight thermoplastic resin and from 10 to 60% of a compatible plasticizer on the surface of the cork and resin particles in a container having flexible, impervious walls, providing a last with a protective covering which will not be affected at the temperatures to which it will be subjected in the process, placing the protected last in the container, positioning the mixture relative to the last to supply a substantial thickness of the mixture at the bottom portion of the last, removing air from the container to shrink the walls and to press them against the last and mixture by atmospheric pressure, heating the container and its contents to a temperature sufiicient to soften the resin, permitting the fine particles of resin to combine with the plasticizer to form a plasticized resinous binder, cooling the container and its contents, permitting air to enter the container, and removing the shaped mixture from the container.

8. The improvement in methods of making inner molds for shoes which comprises heating a mixture comprising from 20 to 65% by weight of 20 to 40 mesh shredded cork, from 15 to of a tough, strong, high molecular weight thermoplastic resin, and from 10 to 60% of a. compatible plasticizer on the surface of the cork and resin particles to a temperature sufficient to soften the resin, compressing the mixture lightly in a billet mold to bond the cork particles together into a porous, coherent mass, placing the mass in a container having flexible, impervious walls, removing air from the container to shrink the walls and press them against the mass of material by atmospheric pressure, heating the evacuated container and its contents to soften the resinous material, shaping the mass by pressing the container and mass therein against a surface reproducing the bottom surface of a foot, cooling the mass, and removing the molded mass from the container.

ERNEST M. CROWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Modern Plastics, page 169, November 1945. 

